In many industries, and in particular, the construction industry, spray application of liquefied compositions has proven very useful. Materials that previously were applied manually may now be applied in a semi-automated fashion using spray systems. For example, at construction sites it is now common for concrete and fire protection coatings to be applied using spray systems.
Spray systems apply materials in slurry or suspension form which then sets after application. A slurry or suspension is typically derived from a powdered material that is mixed with water and/or other liquids and pumped through a conduit to a spray rig where the slurry is sprayed onto a target surface. For example, in a construction setting, a powdered fireproofing material may be mixed with water at the job-site and a slurry comprising the fireproofing material spray-applied to metal building supports.
The term “yield” is used in connection with spray applications systems to refer to the volume of spray-applied slurry composition, after setting, per given weight of dry binder material used to prepare the settable slurry composition. For example, “yield” may refer to the volume of applied fireproofing composition, after setting, per given weight of dry mix used to prepare the fireproofing composition slurry. Yield may be measured in units of board*feet. Manufacturers, designers, contractors, materials suppliers, and others are often interested in the yield that is achieved during a particular job. For example, contractors and materials suppliers may be interested in achieving a particular yield so as to make efficient use of resources.
It is common for accelerating agents to be introduced into compositions in order to have a desired effect on the output of spray application. For example, some accelerating agents or accelerators have the effect of speeding slurry setting time. In other words, the introduction of an accelerator into a slurry may decrease the time needed for a slurry to set after it has been spray-applied.
An accelerator may also have the effect of increasing yield. An increase in yield may be the result of a chemical reaction that occurs between the accelerator and the slurry. For example, an accelerator may have acidic content that reacts upon introduction into a particular slurry. Depending upon the composition or slurry, the reaction may produce a gas such as carbon dioxide. Carbon dioxide and other gases lead to foaming and an expanded slurry composition. An expanded volume of a foamed slurry mixture translates into increased yield upon spray application.